1. Field of the Invention
The present invention relates to: an ultrasonic cleaning apparatus configured to clean an object to be processed, which is immersed in a cleaning liquid, with the use of ultrasonic waves; an ultrasonic cleaning method; and a storage medium storing a computer program for executing the ultrasonic cleaning method.
2. Description of Related Art
There has been conventionally known an ultrasonic cleaning apparatus configured to perform an ultrasonic cleaning (including a megasonic cleaning) of an object to be processed, such as a semiconductor wafer or a glass substrate for LCD, by using ultrasonic waves, with the object to be processed being immersed in a cleaning liquid such as a deionized water or a chemical liquid stored in a cleaning tank (JP2003-209086A). In the ultrasonic cleaning apparatus, a vibrator capable of generating ultrasonic vibration is attached to a bottom part of the cleaning tank, and an ultrasonic oscillator that makes the vibrator ultrasonically vibrate is connected to the vibrator.
When the object to be processed is cleaned in such an ultrasonic cleaning apparatus, the vibrator is made to ultrasonically vibrate by the ultrasonic oscillator, with the object to be processed being immersed in the cleaning liquid in the cleaning tank. Thus, the ultrasonic vibration is propagated to the cleaning liquid, so that particles adhering to the object to be processed are removed. In this manner, the object to be processed is ultrasonically cleaned.
As shown in FIG. 9, there is known an ultrasonic cleaning apparatus 100 including two cleaning tanks 101. In this case, vibrators (not shown) are disposed on bottom parts of the respective cleaning tanks 101, and ultrasonic oscillators 102 are connected to the respective vibrators. When objects to be processed are cleaned, the vibrators are made to ultrasonically vibrate in the cleaning tank 101 in which cleaning steps of the objects to be processed are carried out, by the corresponding ultrasonic oscillator 102.